Magnetic resonance tomography (MRT) or magnetic resonance imaging (MRI) is a known technology for generating images of the interior of the body of a patient based on the physical phenomenon of magnetic resonance (MR). An MR measurement may include a temporal series of rapidly switched gradient pulses and radiofrequency (RF) pulses, which may be defined by an MR sequence.
As a general rule, the gradient pulses are generated during an MR measurement by a gradient coil unit of an MR device and superimposed on a static constant magnetic field. The gradient pulses may cause peripheral nerve stimulations (PNS) in a patient under examination. The RF pulses may be generated by a radiofrequency antenna unit of the MR device and are irradiated into the patient in order to trigger MR signals. The energy of the RF pulses absorbed in this situation per unit of time and per kilogram of body weight is normally referred to as the specific absorption rate (SAR). The absorption of the RF energy may lead to a warming of the body tissue of the patient.
In order to avoid endangering the patient, standardization bodies require that MR measurements comply with strict limit values in respect of their effects. In order to prevent interruptions as a result of exceeding the limit values during the MR measurement, compliance with the limit values may be estimated prior to commencement of the MR measurement. The estimation may be parameterized by a sequence developer defining time ranges to be checked, for example, directly in the code of the MR sequence in order for instance to estimate the nerve stimulations of the patient and/or to calculate the energy absorbed by the patient. On account of a plurality of possible input parameters that influence the MR sequence, the parameterization is not trivial and is therefore also error-prone.
In addition to the limitations described in regard to examining the patient safely, limit values moreover need to be observed which are given by the performance capability of the MR device. For example, the gradient coil unit may only generate a restricted gradient field and the radiofrequency antenna unit may only generate a restricted B1 field.